[Bug lto/55118] New: Missed forward propagation of addresses

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55118

             Bug #: 55118
           Summary: Missed forward propagation of addresses
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hubicka@gcc.gnu.org


When compiling tramp3d we end up overestimating function bodies because many of
array accesses and C++ casts are split into multiple instructions. I.e.:

  _3 = &expr_1(D)->left_m;
                freq:1.00 size:  1 time:  1
                Will be eliminated by inlining
                Accounting size:1.00, time:1.00 on new predicate:(op0 changed)
&& (not inlined)
  _5 = LeafFunctor<Field<UniformRectilinearMesh<MeshTraits<3, double,
UniformRectilinearTag, CartesianTag, 3> >, double, BrickView>, EvalLeaf<3>
>::apply (_3, f_4(D));
                freq:1.00 size:  4 time: 13

here left_m is IMO the first field of the structure so _3 will compile to no
code and should have size 1.  But I do not see why it is not an function
argument.

Other common pattern is 
  _5 = &MEM[(const struct Domain *)&D.660972].D.123571.domain_m[i_4].D.118841;
                freq:3.00 size:  1 time:  1
                Accounting size:1.00, time:3.00 on predicate:(true)
  _6 = &MEM[(struct Domain *)_1(D)].D.123571.domain_m[i_4].D.118841;
                freq:3.00 size:  1 time:  1
                Accounting size:1.00, time:3.00 on predicate:(true)
  _7 = MEM[(const Element_t[2] &)_5];
                freq:3.00 size:  1 time:  1
                Accounting size:1.00, time:3.00 on predicate:(true)

where _5 can be folded into _7 computation.

it is easy to search for "= &" occurences in the dump and most of them are
foldable.

Honza